Locking thread supply case for sewing machines



Dec. 18, 1951 F. ASHWORTH LOCKING THREAD SUPPLY CASE FOR SEWING MACHINES Filed April 2'7, 1949 m i/672107 F050 lam/oar Patented Dec. 18, 1951 LOCKING THREAD SUPPLY CASE FOR SEWING MACHINES Fred Ashworth, Wenham, Mass, assignor to United Shoe Machinery Corporation, Flemington, N. J., a corporation of New Jersey Application April '27, 1949, Serial No. 89,976

2 Claims. 1 The present invention relates to improvements lnlocking thread supply cases for sewing machines, the stitch forming devices of which comprise a curved hook needle and a rotary loop taker acting to cast loops of needle thread over the locking thread case. Examples of such machines are disclosed in United States Letters Patent No.

1 2,203,999, granted July 23, 1940, in the name of flange running about the side surface rotatable within a raceway inside the loop taker, the thread case being retained from rotation with the loop taker by a pair of alternately reciprocating pins engaging notches in the end of the thread case inside the loop taker. To cause each needle loop to be spread uniformly and to begin moving across the inside end of the thread case invariablyat a predetermined rotary position of the loop taker in the said Minett patent, the thread case therein disclosed has an undercut radially projecting thread guiding shoulder on its curved side surface inside the loop taker beyond-the flange of the thread case. The thread is engaged by the should-er as the loop taker begins to carry the needle loop about the thread case and the shoulder arrests movement of one side of the needle loop within the loop taker, raising the side of the needle loop about the inside end of the thread case. As soon as the thread is raisedabove the side of the thread case it is moved across the inside end of the thread case and spread until it reaches a point of maximum extension. Thereafter the needle loop is contracted by a take-up and is released from the thread case.

The undercut thread guiding shoulder of the patented thread case intersects the flange about the side surface of the thread case and is inclined to it in the direction of thread case rotation, its juncture with the thread case inside end being located at a somewhat greater distance from the work than that portion of the shoulder intersecting the flange. For this reason, where the needle loop is not displaced from the base of the shoulder. before the take-up acts, the loop maybe contracted on the thread case about a small section thereon above the position where it is free to be released, causing thread breakage or undesirable abrasion. Such action is particularly noticeable upon the presence of sticky burnt wax at the base of the thread guiding shoulder.

The object of the present invention is to provide a locking thread supply case about which loops of needle thread may be passed with a uniform spreading movement relatively to the rotation of the loop taker and which may thereafter be released from the locking thread case with certainty sooner than heretofore considered possible, thus aiding generally the facility with which the machine operates and providing more time during each sewing cycle in which the other stitch forming and thread handling devices may operate. To this end the discoidal locking thread supply case is formed in the usual manner with flat end and curved side surfaces, a circular flange being provided about the side surface rotatable within the raceway in the loop taker and the thread guiding shoulder extending from the flange to the end surface at an inclination to the flange, in which the inner edge of the thread case near the base of the thread guiding shoulder, as embodied in the machine of the present invention, is made with a relatively straight ledge, preferably tangent to the curved side surface at the point where each needle loop contracts, to enable uniform release of the needle loop from the thread case while the loop engages the base of the shoulder and substantially before the loop taker carries the loop to a diarnetric position across the thread case inner end. Not only does the use of a straight tangent ledge 0n the thread case at the base of the thread guiding shoulder insure uniform release under all circumstances of each needle loop but it adds to the strength and durability of the thread case and resists the wearing action of the thread on the thread case side surface; Actually the needle loop may be drawn from the thread case with certainty at least 10 of rotation in the main sewingshaft, sooner than is possible in the prior machine.

These and other features of the invention as hereinafter described and claimed will be apparent from the following detail description taken inconnection with the accompanying drawings, in which Fig. 1 is a detail view in side elevation, looking from the left of so much of a lockstitch sewing machine as is necessary to illustrate the embodiment of the present invention;

Fig. 2 is a front sectional view on an enlarged scale of the loop taker and thread case as viewed along the line IIII of Fig. 1, looking from the right side of the machine and indicating the relationship with the work, a needle loop being indicated in dot-dash lines in a position just before and in full lines just after being released from the thread case;

Fig. 3 is a side detail view partly in section of the loop taker, thread case and presser foot; and

Fig. 4 is a detail view on a still further enlarged scale looking from the front of the righthand portion of the improved locking thread supply case.

The machine illustrated in the drawing is of substantially the same construction and manner of operation, except as hereinafter pointed out,-

as that disclosed in the patents referred to. The machine includes a curved hook needle 10, a work support 12, a presser foot M, a rotary loop taker or shuttle 16, a thread case It, a take-up l9, and other stitch forming and work feeding devices. The loop taker consists of a hollow cylindrical body having a circular opening, a rotary hook or beak, the tip 28 of which is arranged to enter each needle loop indicated at 22 and to carry each loop about the thread case 18. The loop taker is also formed with two guiding grooves or raceways 24 and 26, one outside and one inside for rotatably Supporting the loop taker in the machine frame and for supporting the thread case 18 within the loop taker respectively. I

The thread case is discoidal in shape and has a cylindrically curved side surface between two substantially flat end surfaces, one end surface 28 and a portion of the side surface extending inside the opening of the loop taker beyond the raceway 26. The side surface also has a flange 30 engaging the raceway 26. For holding the thread case from rotation with the loop taker a pair of alternately reciprocating pins 32 are provided slidingly mounted in a fixed part of the machine and spring actuated into slots 34 at the inner end of the thread case, each pin being lifted to clear the needle loop as it passes across the inner'end of the thread case.

The tip 20 of the loop taker beak is so arranged that in engaging the needle loop and carrying it about the thread case it gives the needle loop a half twist. As in the machine of the Minett patcut the thread case flange 3D has a hook or notch 36 at one end to assist the loop taker beak in the notch 36 and to prevent both sides of the l loop from being wound about the curved side surface of the thread case the thread case side surface is undercut, forming an abrupt radially pro-- jecting thread guiding shoulder 38 extending from the flange 30 through the inner end 28 of the thread case. As the notch 36 is engaged by the needle loop the latter is carried up the guiding shoulder to the point of intersection of the shoulder with the thread case end 28 where it immediately starts to move across the end. To assist in raising the needle loop to the surface 28 of the end the shoulder 38 has a base 29 inclined from the flange to the surface 28 of the end in the direetion of thread case rotation as illustrated in Fig. 3. In moving across the end surface 28 of the thread case the loop of needle thread is em larged until it reaches a position of maximum extension after which the take-up l8 begins-to con tractthe needle1oQp-- g 'Oi1 account of the inclination of the; thread guiding shoulder 38 the upper end of the shoulder where it intersects the thread case end surface 28 engages the needle loop before the loop reaches a position of maximum extension and is retained in engagement with the shoulder at its base 29 occasionally even after the point of maximum extension of the needle loop is reached. Under these circumstances the take-up in contracting,

the needle loop may tension the thread sufficiently to cause breakage on the thread case or at tion. where it becomes tangent to the curved side.

surf-ace of the thread case. When the needle loop engages the tangent point of the ledge 40 the needle loop is free to contract and be released normally on the thread case. The ledge 40 is formed by the intersection of a fillet for the base of the shoulder 38 and the inner end surface 28 of the thread case. Even though the thread in the needle loop is retained in engagement with the base 29 of the thread guiding shoulder 38 the take-up in contracting the needle loop will draw it along the ledge 40 to the point of tangency of the ledge with the curved side surface of the thread case, the ledge camming the thread away from the base of the shoulder. Accordingly, it is possible to adjust the take-up so that it acts somewhat earlier in each sewing cycle than without the straight ledge on the thread case.

Referring more particularly to Fig. 2 of the drawings, during rotation of the loop taker l6 each needle loop is carried to a position in which the thread extends from the thread guiding shoulder 38, as shown in the dot-dash lines, to a position where the thread engaging the end surface of the thread case nearly reaches a diametrical position, shown in full lines. At the full line position the loop is definitely free for normal release from the thread case. The movement of the loop from the dot-dash position to the full line position occurs during a relatively small rotation of the loop taker. V

In the prior machine if for any reason the thread were retained in the dot-dash position when the take-up acts to tension the thread there is likelihood of the thread being damaged or broken. With the use of the straight tangent ledge as on the thread case such damage or breakage is avoided since there is no tendency for the contracting needle loop to become tightened on a section of the thread case which is smaller than the section defined by the full-line position, the section defined by the dot-dash position being larger. Thus, the needle loop moves from the dot-dash position to the final released solid line position freely.

The nature and scope of the invention having been indicated and a particular embodiment having been described, what is claimed is:

l. A lockstitch sewing machine having a'hook needle, a rotary loop taker having a circular opening and a raceway inside the opening, a disc-oidal thread case having substantially flat end and curved side surfaces and a circular flange about the side surface rotatable within the racewayin the loop taker, the end and curved side surfaces extendingginside the, op nin the loopv taker beyond ,the. raceway, and-:a radially projecting thread guiding shoulder on the curved side surface of the thread case inside the loop taker beyond the flange of the thread case having a base inclined from the flange to said end surface in the direction of thread case rotation for causing the needle loop to begin moving across the end surface of the thread case invariably at a predetermined rotary position of the loop taker, in combination with a straight ledge extending along said thread case side surface from the base of the thread guiding shoulder to enable uniform movement of the needle 100p under tension about the thread case While the loop engages the base of the shoulder.

2. A lockstitch sewing maching having the combination of claim 1 in which the loop releasing ledge of the thread case is tangent to the curved side surface at the point where the needle loop contracts freely for normal release from the thread case.

FRED ASHWORTH.

REFERENCES CITED UNITED STATES PATENTS Name Date Minett July 23, 1940 Number 

